Materials and substrates containing free amino groups are subject to stain by certain natural and artificial colorants found in foods and other consumer products. The addition of stain resistant characteristics to substrates containing free amino groups provides a more desirable end product for the consumer.
Substrates, including fibers containing free amino groups, such as polyamide fibers, can be made stain resistant to certain stains by contacting the substrate with a solution containing an anionically modified phenol formaldehyde polymer, phenol sulfonates and their derivatives, naphthalene condensates, or blends of these materials. It is also known to blend these materials with polyether polymers, vinyls, polycarbonate polymers, and ethylene polymers.
One method of imparting stain resistance to fibers containing free amino groups is disclosed in U.S. Pat. No. 4,699,812 (Munk et al.). U.S. Pat. No. 4,699,812 discloses a process for imparting stain resistance in which a solution of aliphatic sulfonic acid is applied to the fibers, which are then dried.
U.S. Pat. No. 4,592,940 (Blyth et al.) discloses a process for imparting stain resistance to nylon fibers, in which the fibers are treated with the condensation products of formaldehyde and a mixture of diphenolsulfone and phenolsulfonic acid. The substrate is treated by immersing the carpet in the boiling treatment solution at a pH of 4.5 or less.
U.S. Pat. No. 4,822,373 (Olson et al.) discloses a process for treating polyamide materials in which a fibrous polyamide substrate is treated with a combination of (a) a partially sulfonated phenol formaldehyde polymer and (b) polymethacrylic acid, copolymers of methacrylic acid, or combinations of polymethacrylic acid and copolymers of methacrylic acid. The solution is generally applied as an aqueous solution at a pH below about 7.
U.S. Pat. No. 4,940,757 (Moss, III et al.) discloses a stain resistant polymeric composition for fibers having polyamide linkages. The composition is prepared by polymerizing an α-substituted acrylic acid in the presence of a sulfonated aromatic condensation polymer. The composition is applied to the substrate via flood, spray, foam methods, etc.
Additionally, U.S. Pat. No. 3,949,124 (Jilla) discloses a method and composition of imparting soil-repellency and antistatic properties. The reference discloses the pretreatment of a substrate with a material containing the condensation products of formaldehyde and another component chosen from a wide variety and long list, some of which are sulfonated phenol, diaryl sulfone, urea, melamine and dicayndiamide, followed by heat treatment and application of a separate composition containing, as one ingredient, a water-dispersible polyester and amino polymer followed by another heat treatment. U.S. Pat. No. 3,949,124 concerns imparting antistatic and antisoiling properties, which are distinct from stain resistance.
Those skilled in the art recognize that while anionically modified phenol formaldehyde polymers, napthalene condensates, lignin sulfonates and phenol sulfonate derivatives provide stainblocking, their photo instability causes yellowing of the dyed substrate over time. Therefore, there exists a need for compositions and methods that provide excellent stain resistance, while at the same time exhibiting reduced photo instability, i.e. reduced yellowing.